Lecture 1: Introduction To Physiology And Homeostasis PDF

Lecture 1 Introduction To Physiology And Homeostasis DR RAZI  Desired Learning Outcomes:- 1. define homeostasis. 2. explain feedback mechanisms. 3. state examples of feedback mechanisms. 27 Introduction to Physiology Physiology is...

Lecture 1 Introduction To Physiology And Homeostasis DR RAZI  Desired Learning Outcomes:- 1. define homeostasis. 2. explain feedback mechanisms. 3. state examples of feedback mechanisms. 27 Introduction to Physiology Physiology is the study of the functions of living things. Focus on how the human body works. Physiology focuses on mechanisms of action. Two approaches are used to explain events that occur in the body; 1. purpose of a body process and 2. underlying mechanism by which this process occurs. Example: “Why do I shiver when I am cold?” Purpose: “to help my body warm up, because shivering generates heat.” Underlying mechanism: explanation of shivering is that when temperature-sensitive nerve cells detect a fall in body temperature, they signal the area in the brain responsible for temperature regulation. In response, this brain area activates nerve pathways that ultimately bring about involuntary, oscillating muscle contractions (that is, shivering). Structure and function are inseparable. Physiology is closely related to anatomy, the study of the structure of the body Some structure–function relationships are obvious. For example, the heart is well designed to receive and pump blood, the teeth to tear and grind food, and the hingelike elbow joint to permit bending of the arm. The respiratory airways, which carry air from the outside into the lungs, branch extensively when they reach the lungs. Tiny air sacs cluster at the ends of the huge number of airway branches. The branching is so extensive that the lungs contain about 300 million air sacs. Levels of Organization in the Body The chemical level: Various atoms and molecules make up the body The cellular level: Cells are the basic units of life. The tissue level: Tissues are groups of cells of similar specialization. The organ level: An organ is a unit made up of several tissue types. The body system level: A body system is a collection of related organs. The organism level: The body systems are packaged into a functional whole body Four primary types: muscle, nervous, epithelial, and connective  Concept of Homeostasis The external environment is the surrounding environment in which an organism lives. The internal environment is the fluid that surrounds the cells and through which they make life-sustaining exchanges. The fluid collectively contained within all body cells is called intracellular fluid (ICF). The fluid outside the cells is called extracellular fluid (ECF). ECF is made up of two components: the plasma, the fluid portion of the blood, and the interstitial fluid, which surrounds and bathes the cells (inter means “between”; stitial means “that which stands”) Homeostasis Homeostasis (homeo means “similar”; stasis means “to stand or stay”) is termed maintenance of a relatively stable internal environment. Homeostasis is essential for the survival of each cell, and each cell, through its specialized activities as part of a body system, helps maintain the internal environment shared by all cells. The 11 body systems contribute to homeostasis Homeostatically Regulated Factors Factors of the internal environment must be homeostatically maintained: 1. Concentration of nutrients. 2. Concentration of O2 and CO2. 3. Concentration of waste products. 4. pH. 5. Concentrations of water, salt, and other electrolytes. 6. Volume and pressure. 7. Temperature. Homeostatic Control Systems To maintain homeostasis, the control system must be able to : (1) detect deviations from normal in the internal environmental factor that needs to be held within narrow limits; (receptor/sensor) (2) integrate this information with any other relevant information; (Integrating center) and (3) make appropriate adjustments in the activity of the body parts responsible for restoring this factor to its desired value; (Effector) Homeostatic control systems may operate : locally(intrinsic) or bodywide/extrinsic (systemic) Extrinsic control of the organs and body systems is accomplished by the nervous and endocrine systems, Control systems 1. Negative feedback opposes an initial change and is widely used to maintain homeostasis control of body temperature 2. Positive feedback amplifies an initial change. In the birth of a baby. The hormone oxytocin causes powerful contractions of the uterus (womb). As the contractions push the baby against the cervix (the exit from the uterus), the resultant stretching of the cervix triggers a sequence of events that brings about the release of even more oxytocin, which causes even stronger uterine contractions, triggering the release of more oxytocin, and so on. This positive- feedback cycle does not stop until the cervix is stretched sufficiently for the baby to be pushed through and born 3. Feedforward mechanisms initiate responses in anticipation of a change. For example, when a meal is still in the digestive tract, a feedforward mechanism increases secretion of a hormone (insulin) that promotes the cellular uptake and storage of ingested nutrients after they have been absorbed from the digestive tract. This anticipatory response helps limit the rise in blood nutrient concentration after nutrients have been absorbed. Positive feedback Disruptions in homeostasis can lead to illness and death. The term pathophysiology refers to the abnormal functioning of the body (altered physiology) associated with disease. Many diagnostic tests rely heavily on principles learned by physiologists; examples include the electrocardiogram and lung function tests. Treatments for a number of pathophysiological conditions, such as high blood pressure, diabetes mellitus, and erectile dysfunction, are likewise based on knowledge acquired through physiological research. Thus physiology is at the heart of clinical practice.  Tutorial Questions 1. List and describe the levels of organization in the body. 2. Name the four primary types of tissue and give an example of each. 3. Distinguish among external environment, internal environment, intracellular fluid, extracellular fluid, plasma, and interstitial fluid. 4. Define homeostasis 5. Compare negative feedback and positive feedback. 6. Body temperature is homeostatically regulated around a set point. Given your knowledge of negative feedback and homeostatic control systems, predict whether narrowing or widening of the blood vessels of the skin will occur when a person exercises strenuously. (Hints: Muscle contraction generates heat. Narrowing of the vessels supplying an organ decreases blood flow through the organ, whereas vessel widening increases blood flow through the organ. The more warm blood flowing through the skin, the greater is the loss of heat from the skin to the surrounding environment.) Thank you